Means of coupling energy to or from a coaxial resonator



NOV- 20, 1956 A. M. BucKsBAuM MEANS OF COUPLING ENERGY TO OR FROM A COAXIAL RESONATOR Filed Jne 7. 1952 v INVENTOR. 4F/vala M farms-40M vBY 2M 2&4/

/IT rok/vir UnitedStates VPatent yO 2,771,516 f t or coUrLlNG ENERGY To oRERoM A coAXIAL RESONATOR `Arnold M. Bucksbaum, Grinnell, Iowa, assigner to Col- Vlins Radio Company, CedarfRapids, Iowa, a corpora- ,tion oflowa Application June 7, '1952, Serial No.292,341 2Claims. (Cl. 1*79--171) This inventiontrelates in lgeneral'to coupling means and in particular-to means forcoupling high frequency energy from a coaxial resonator.

-It has been customary previously to couple energy from a coaxial resonator by using capacity probes which couple to the electric iield vor alternatively, by vusing inductive probes which couple to the magnetic iield. The disadvantage of such coupling devicesis that they distort the electric and magnetic fields. v t

It is an object of this invention, therefore, to provide means for coupling energy to or from a cavity resonator in ia manner vsuch that the 4electrical and magnetic lields arenotdistorted. p t p `.Yet vanother object of this invention is to :provide an improved coupling means 'for a ,cavity resonator wherein .the coupling is symmetrical with respect to the cavity and `thus does not substantially distort the magnetic or elec- .tricallields VA "further object of this invention is .to provide an improved coupling means which is,"in eifect, an improved impedance matching means for use at high frequencies.

A feature of this invention is found in the provision for a coupling condenser mounted concentrically about one edge of a high frequency resonator so as to couple energy to or from an external line.

Further features, objects and advantages of the invention will become apparent from the following description and claims when read in View of the drawings, in which:

Figure 1 is a sectional view of a coaxial resonator mounted concentric with a coaxial line according to the principles of this invention;

Figure 2 is a schematic equivalent circuit of the coupling means of this invention.

Figure 3 is a practical embodiment illustrating the use of the principles of this invention in conjunction with a high frequency tube; and

Figure 4 is a schematic diagram of the structure shown in Figure 3.

Figure 1 illustrates a ground plane 10 which might, for example, be a copper plate to which is connected the outer conductor 11 of a coaxial transmission line 40. The inner conductor comprises a cylinder 12 mounted concentrically within the member 11 and which has its bottom end 13 connected to an annular insulator 14 that is attached to the plate 10. The insulator or dielectric 14 forms a capacitance between the end of the inner conductor of the transmission line and the ground plane 10.

Mounted concentrically within the inner conductor 12 is a shaft 15 which may be hollow or solid as desired. lt is supported by a conducting annular member 16. The lower end 17 of the shaft 15 terminates above the plate 10. An upwardly extending stub 18 is attached to the plate and extends to a point near the end 17. 'Ihe stub 18 might be adjustable relative to the end 17 so as to vary the capacitance between the shaft and ground.

The space between the shaft 15 and the inner conductor 12 below the annular member 16 forms a cavity Patented Nov. '20, 11956 2 V resonator 41 whose frequency is .determinedtbyfthetposition of the annular member `16. `Inner conductor 12;,is therefore a common wall between resonator 41 and transmission line 40.

Energy may be coupled to or from the cavityresonator 41 thus formed .by attaching an yinput or output---linerto the coaxial transmission line 40 comprising .the outer conductor 11 and rtheinner conductorj12 It is to be realized, of course, that the physical `dimensions of an inputfor output line which might -be connected to the transmission line may be `varied infoutside diameter in a fashion well known to those skilled inthe art. In general the ratio of the diametersv of :the .inner1and outer conductors is maintained-constant.

Figure 2 is an equivalent circuit for the structure shown in `Figure 1 wherein a resistor R1 Y:represents the resistive `impedance of Xo1 `on lthe circuit, where Cris the capacitance between the `stub 18 and `the'end of athe line 15. The resistance R2 represents the characteristic impedanceof the transmission line -formed by 11 `and .112, and the XCR represents the capacitive impedance `of the capacitance formed by the-insu1ator'14.

It is yto be noted that'the condenser formed .by the insulator 14 establishes a symmetrical Apattern with Arespect to the ycavity resonator so as to assure Vthatthe magnetic Vand electrical "iields `contained within the resonator .will

`cooling `vanes attached thereto through .which a coolant is forced to dissipate the heat generated.

The plate 10 has a cylindrical member 19 mounted thereon and an inner cylindrical member 20 which is insulated from the plate 10 by an insulation or dielectric ring 21 to form a cavity resonator 42. An annular conducting plunger 22 is mounted between the member 19 and 20 to tune it. Instead of connecting the coaxial cable to the upper ends of the members 19 and 20 as in Figure l, the outer conductor 19 may be attached to a second outer conductor 23 which extends from one side and the inner conductor 20 may be connected to a second inner conductor 24 which extends transversely from the member 20 and through the outer conductor 23 to form a coaxial waveguide 44.

An inner cylindrical member 25 is supported from the member 20 by a disc 26 and terminates above the plate 10. A plunger 27 is annular in shape and is received between the member 20 and the member 25 so as to tune the cavity resonator 43 thus formed.

The plate 28 of the tube 29 is received within a metal sleeve 30 which is held by an .insulative sleeve 31 that is connected to the inside of the member 25. The grid 32 of the tube is connected to a condenser C3 and an inductor L1 which is in turn coupled to an input inductor L2. The screen grid 33 of the tube is mounted in a metallic conductive disc 34 which is insulated from the plate 10 by an insulator 35.

The insulation 35 forms a capacitance C4 to ground. The cathode of the tube is connected to pins 36, one of which is grounded, and the other is connected to a heating potential. The screen grid is connected to B plus through a resistor R3.

The equivalent circuit of the `structure shown in Fgure 3 is shown in Figure 4 wherein like numerals refer to both figures. The plate 28 is connected to B plus through an inductor L3.

The tube as illustrated may be used as an amplifier whereln the input supplied across the inductor L2 varies the amplitude of the r. f. energy produced in the cavity resonator by the tube 29. `The energy Ygenerated'in the metrical vfashion and in a manner not previously known. Although the invention has been described with respect to particular embodiments thereof, it is not to be so limited as changes and modifications may be made therein which are Within the full intended scope of the invention as delined by the appended claims.

I claim:

`l. A symmetrical coupling system comprising, a ground plate, a iirst hollow cylindrical member connected to said `ground plate and forming the outer conductor of a coaxial transmission line, a second hollow cylindrical member supported within the rst cylindrical member and forming the inner conductor of a coaxial transmission line, an annular insulator attached between said ground plate and the lower'end of said second cylindrical member' to symmetrically pass electrical wave energy, a rst tuning plunger generally annular in shape mounted between the first and second cylindrical members, a disc mounted within the second cylindrical member, an inner `cylindrical member attached to said disc and extending `downwardly therefrom, a second tuning plunger mounted between the inside of the second cylindrical member and `said inner cylindrical member to tune the cavity resonator'thus formed, means for injecting energy into said cavlty resonator, anv output coaxial line comprised of a first transverse cylindrical member attached to the rst Acylindrical member, and a second inner transverse conductor attached to the second cylindrical member and 4 passing concentrically through the first transverse member, said coupling system providing an impedancevmatch between said energy injection means and said output coaxial line.

2. Means for eiciently coupling an electron tube to an youtput coaxial line comprising, a ground plate, a rst hollow conducting cylindrical member attached to said ground plate, a second hollow conducting cylindrical member mounted concentrically within said rst cylindrical member, an annular dielectric member attached between an end of said second cylindrical member and said ground plate, a disc mounted Within said second hollow cylindrical member, an inner conducting cylindrical member attached to said disc and extended toward said ground plate, a rst tuning plunger generally annular in shape mounted between said lirst and second cylindrical members, a second tuning plunger annular in shape mounted between said second cylindrical member and said inner cylindrical member, the outer conductor of said output coaxial line connected transversely to said iirst cylindrical member, and the inner conductor of said output coaxial line connected transversely to said second cylindrical conductor, said electron tube coaxially supported with its plate connected to said inner cylindrical member and its grid connected to said ground plate, whereby an impedance match is obtained between said coaxial line and the plate of said tube by tuning said plungers.

References Cited inthe lile of this patent UNITED STATES PATENTS 2,169,305 Tuniek Aug. l5, 1939 2,443,908 Gurewitsch June 22, 1948 2,472,204 Fubini et al .Tune 7, 1949 2,525,901 Hansen et al Oct. 17, 1950 2,554,501 Preist May 29, 1951 2,641,657 Preist et al June 9, 1953 2,641,658 Preist June 9, 1953 

